The invention relates to a meat deboning sieve for use in a mechanical apparatus and process for deboning the meat portion of poultry, fowl and the like by forcing a meat and bone material through a pressure housing with gradually increasing force so that the meat is separated by the sieve while the bony material exits an end of the sieve.
Prior deboning apparatus and methods, for example, as shown in U.S. Pat. No. 4,042,176, cause a separation of bony material from the meat of poultry and the like. An auger forces the material through a pressure housing where the meat is forced outwardly through a perforated screen and the bony material is forced axially through the pressure housing where it exits. The apparatus and method of this type have a high temperature rise in the pressure housing due to high pressures and relatively high friction losses as the product passes through the perforated screen. The meat product remains inside the pressure housing for a long time at high pressures. This causes seals in the infeed area to regularly leak. Due to the small hole area of the perforations in the screen, typically the size of a 0.5 mm pencil lead drilled in the screen, the fiber length of the meat product passing through the screen is reduced. The high temperature rise and high pressure in the pressure housing produce a relatively high bone count and fat content, in addition to a reduced shelf life of the meat product. The perforated screen has a relatively short life.
U.S. Pat. Nos. 4,685,626 and 4,340,184 disclose other forms of separator screens for use in meat deboning apparatus and method employing "slotted" screens. The first patent ('626) discloses a separation grill forming a sieve which includes a spiral spring having wedges disposed between adjacent windings to from spiral slots through which meat may be separated under pressure. The second patent ('184) discloses a separator screen which includes a stack of plain annular discs alternating with configured annular discs which are clamped tightly face to face. The configured discs include a reduced web surrounding spacer portions. When the discs are clamped together, slots are defined between the plain discs and the reduced webs of the configured discs through which the meat passes for separation during pressurization. The slots are not regularly defined in a manner in which a continuous passage of meat is provided through the ring without a change in direction. However, the assembly of many rings held in position by a cage results in internal voids being formed which can harbor bacteria. Because of these voids, the screens must be disassembled regularly for cleaning. Not only do these type of screens have to be disassembled for cleaning on a regular basis, but they must be sharpened regularly while they are disassembled, due to the relative soft nature of the metal used. This creates metal filings and burrs caused by the soft stainless steel with poor edging qualities used in its construction. The slotted screen constructions also have been found to allow excessive bone count, particularly at high speed operation. Because the slots are not machined at angles, the material must change direction as it leaves the slot, increasing turbulence and temperature rise.
Accordingly, an object of the invention is to provide a sieve for a meat deboning apparatus and method which provides increased production of meat product.
Another object of the invention is to provide a sealed one-piece construction for a meat deboning sieve for a mechanical deboning apparatus and method which produces a meat product with lower bone and fat content at higher production rates.
Another object of the invention is to provide a sieve for deboning meat having a unitized construction which eliminates voids which harbor bacteria and does not require cleaning or sharpening on a regular basis, and does not require disassembly.
Another object of the present invention is to provide a cylindrical sieve for deboning meat which includes slots that extend radially from a center of the sieve to facilitate separation of the meat without significant change in direction through the sieve.
Another object of the invention is to provide a deboned meat product with longer fibers.
Another object of the invention is to provide a meat deboning sieve which operates at a lower pressure and produces a lower temperature rise in the meat product.
Another object of the invention is to provide a cylindrical meat deboning sieve which reduces the bone count and fat content in the meat product at a bone exit end of the sieve.